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NAME

       DS1825 - Programmable Resolution 1-Wire Digital Thermometer with ID

       MAX31826
              - Digital Temperature Sensor with 1Kb Lockable EEPROM

       MAX31850 MAX31851
              - Cold-Junction Compensated Thermocouple

SYNOPSIS

   Thermometer with hardware address pins (DS1825)
       3B  [.]XXXXXXXXXXXX[XX][/[  fasttemp  |  temperature  |  temperature9  |  temperature10  |
       temperature11 | temperature12 | latesttemp | power | prog_addr  |  temphigh  |  templow  |
       tempres | address | crc8 | id | locator | r_address | r_id | r_locator | type ]]

   Digital Temperature Sensor with 1Kb Lockable EEPROM (MAX31826)
       3B    [.]XXXXXXXXXXXX[XX][/[    temperature    |   latesttemp   |   power   |   memory   |
       pages/page.[0-15|ALL] | prog_addr | address | crc8 | id | locator |  r_address  |  r_id  |
       r_locator | type ]]

   Cold-Junction Compensated Thermocouple (MAX31850 and MAX31851)
       3B [.]XXXXXXXXXXXX[XX][/[ temperature | latesttemp | thermocouple | fault | open_circuit |
       ground_short | vdd_short | power | prog_addr | address | crc8 | id | locator | r_address |
       r_id | r_locator | type ]]

FAMILY CODE

       3B

SPECIAL PROPERTIES

   power
       read-only,yes-no
       Is the chip powered externally (=1) or from the parasitically from the data bus (=0)?

   prog_addr
       read-only, 0-15
       A  distiguishing  feature  of  the  DS1825  (3) is the ability to set hardware pins for an
       address (0-15). This is an alternative to the unique 64-bit address that  is  set  in  the
       factory.

   temperature
       read-only, floating point
       Measured temperature with 12 bit resolution.

       For the MAX31850 MAX 31851 this is the cold-junction temperature -- the temperature at the
       chip. See thermocouple

   temperature9 temperature10 temperature11 temperature12
       read-only, floating point ( DS1825 only)

       Measured temperature at 9 to 12 bit  resolution.  There  is  a  tradeoff  of  time  versus
       accuracy in the temperature measurement.

       The  MAX31826  MAX31850  MAX31851  measure  all  temperatures at 12 bit resoltion and will
       return that resolution to all the possible temperature properties.

   latesttemp
       read-only, floating point
       Measured temperature at 9 to 12 bit resolution, depending on the resolution of the  latest
       conversion  on  this  chip. Reading this node will never trigger a temperature conversion.
       Intended for use in conjunction with /simultaneous/temperature.

   fasttemp
       read-only, floating point
       Equivalent to temperature9

   thermocouple
       read-only, floating point ( MAX31850 MAX31851 only)

       Measured temperature of the thermocouple at 16bit  resolution.  Cold-junction  temperature
       compensated.

       The  actual  thermocouple  type  used  is  set  by  the  selected  chip  type,  and is not
       discoverable in software.

TEMPERATURE ALARM LIMITS

       When the device exceeds either temphigh or templow temperature threshold the device is  in
       the alarm state, and will appear in the alarm directory. This provides an easy way to poll
       for temperatures that are unsafe, especially if  simultaneous  temperature  conversion  is
       done.

       Units  for  the  temperature  alarms  are  in  the same temperature scale that was set for
       temperature measurements.

       Temperature thresholds are stored in non-volatile memory and persist until  changed,  even
       if power is lost.

   temphigh
       read-write, integer
       Shows or sets the lower limit for the high temperature alarm state.

   templow
       read-write, integer
       Shows or sets the upper limit for the low temperature alarm state.

       The MAX31826 does NOT have temperature thresholds and temperature alarm.

TEMPERATURE RESOLUTION DEFAULT VALUE

   tempres
       read-write, integer
       The  device  employs a non-volatile memory to store the default temperature resolution (9,
       10, 11 or 12 bits) to be applied after power-up. This is useful if  you  use  simultaneous
       temperature  conversions. Reading this node gives you the value stored in the non-volatile
       memory. Writing sets a new power-on resolution value.

       As a side effect, reading this node resets the temperature resolution used by simultaneous
       temperature  conversions  to its power-on value. It also affects the resolution value used
       by latesttemp, to scale the latest  conversion  value,  so  make  sure  to  re-sample  the
       temperature before accessing latesttemp after writing or reading the tempres value.

MEMORY

       Only the MAX31826 supports memory functions.

   pages/page.0 .. pages/page.15 pages/page.ALL
       read/write, binary
       EEPROM memory pages of 8 bytes each. See the datasheet about locking contents.

   memory
       read/write, binary
       EEPROM memory of 128 bytes. See the datasheet about locking contents.

FAULT REPORTING

       Only the MAX31850 MAX31851 supports fault reporting.

   fault
       read-only, yes-no
       Fault in last thermocouple conversion

   open_circuit
       read-only, yes-no
       Thermocouple leads disconnected.

   ground_short
       read-only, yes-no
       Thermocouple lead shorted to ground.

   vdd_short
       read-only, yes-no
       Thermocouple lead shorted to supply voltage.

STANDARD PROPERTIES

   address
   r_address
       read-only, ascii
       The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).
       address starts with the family code
       r  address  is the address in reverse order, which is often used in other applications and
       labeling.

   crc8
       read-only, ascii
       The 8-bit error correction portion.  Uses  cyclic  redundancy  check.  Computed  from  the
       preceding  56  bits of the unique ID number. Given as upper case hexadecimal digits (0-9A-
       F).

   family
       read-only, ascii
       The 8-bit family code. Unique to each type of device.  Given  as  upper  case  hexadecimal
       digits (0-9A-F).

   id
   r_id
       read-only, ascii
       The  48-bit  middle  portion  of the unique ID number. Does not include the family code or
       CRC. Given as upper case hexadecimal digits (0-9A-F).
       r id is the id in reverse order, which is often used in other applications and labeling.

   locator
   r_locator
       read-only, ascii
       Uses an extension of the 1-wire design from iButtonLink  company  that  associated  1-wire
       physical connections with a unique 1-wire code. If the connection is behind a Link Locator
       the locator will show a unique 8-byte number  (16  character  hexadecimal)  starting  with
       family code FE.
       If no Link Locator is between the device and the master, the locator field will be all FF.
       r locator is the locator in reverse order.

   present (DEPRECATED)
       read-only, yes-no
       Is the device currently present on the 1-wire bus?

   type
       read-only, ascii
       Part  name  assigned  by Dallas Semi. E.g.  DS2401 Alternative packaging (iButton vs chip)
       will not be distiguished.

DESCRIPTION

   1-Wire
       1-wire is a wiring protocol and series of devices  designed  and  manufactured  by  Dallas
       Semiconductor,  Inc.  The bus is a low-power low-speed low-connector scheme where the data
       line can also provide power.

       Each device is uniquely and unalterably numbered during  manufacture.  There  are  a  wide
       variety  of  devices,  including memory, sensors (humidity, temperature, voltage, contact,
       current), switches, timers and data  loggers.  More  complex  devices  (like  thermocouple
       sensors)  can  be  built with these basic devices. There are also 1-wire devices that have
       encryption included.

       The 1-wire scheme uses a single bus master and multiple slaves on the same wire.  The  bus
       master  initiates  all  communication.  The  slaves  can  be  individually  discovered and
       addressed using their unique ID.

       Bus masters come in a variety of configurations including serial, parallel,  i2c,  network
       or USB adapters.

   OWFS design
       OWFS  is  a  suite of programs that designed to make the 1-wire bus and its devices easily
       accessible. The underlying principle is to create a virtual filesystem, with the unique ID
       being the directory, and the individual properties of the device are represented as simple
       files that can be read and written.

       Details of the individual slave or master design are hidden behind a consistent interface.
       The  goal  is to provide an easy set of tools for a software designer to create monitoring
       or control applications. There are some performance enhancements  in  the  implementation,
       including  data  caching,  parallel  access  to  bus  masters,  and  aggregation of device
       communication.  Still  the  fundemental  goal  has  been  ease  of  use,  flexibility  and
       correctness rather than speed.

   DS1825
       The  DS1825  (3)  is one of several available 1-wire temperature sensors. Alternatives are
       the DS18S20 (3), DS18B20 (3), and DS1822 (3) as well as  temperature/voltage  measurements
       in  the  DS2436 (3) and DS2438 (3).  For truly versatile temperature measurements, see the
       protean DS1921 (3) Thermachron (3).

       The  DS1825  (3)  can  select  between  4  resolutionsspanning  the  fastest/roughest  and
       slowest/best.

   MAX31826
       The  MAX31826  shares  a  family  code  with the DS1825 but has differences in some of its
       functions.

       The MAX31826 has 128 btes of EEPROM memory (as 16 pages of 8 bytes) while the  DS1825  has
       no memory available.

       The  MAX31826  measures  temperature  at  12 bit resolution as fast as the DS1825's lowest
       resolution (and always uses 12-bit resolution). On the other hand it  has  no  temperature
       thresholds or alarm function.

ADDRESSING

       All  1-wire  devices  are factory assigned a unique 64-bit address. This address is of the
       form:

       Family Code
              8 bits

       Address
              48 bits

       CRC    8 bits

       Addressing under OWFS is in hexadecimal, of form:

              01.123456789ABC

       where 01 is an example 8-bit family code, and 12345678ABC is an example 48 bit address.

       The dot is optional, and the CRC code can included. If included, it must be correct.

       Both the MAX31826 and the DS1825 allow hardware selection of part of  the  address,  which
       can assist selecting between chips is some circuit designs.

DATASHEET

       DS1825 http://pdfserv.maxim-ic.com/en/ds/DS1825.pdf

       MAX31826
              http://datasheets.maxim-ic.com/en/ds/MAX31826.pdf

SEE ALSO

   Programs
       owfs  (1)  owhttpd  (1) owftpd (1) owserver (1) owdir (1) owread (1) owwrite (1) owpresent
       (1) owtap (1)

   Configuration and testing
       owfs (5) owtap (1) owmon (1)

   Language bindings
       owtcl (3) owperl (3) owcapi (3)

   Clocks
       DS1427 (3) DS1904 (3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)

   ID
       DS2401 (3) DS2411 (3) DS1990A (3)

   Memory
       DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995  (3)  DS1996  (3)
       DS2430A (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS28E04 (3) DS28EC20 (3)

   Switches
       DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3)

   Temperature
       DS1822  (3) DS1825 (3) DS1820 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821 (3)
       DS28EA00 (3) DS28E04 (3) EDS0064 (3) EDS0065 (3)  EDS0066  (3)  EDS0067  (3)  EDS0068  (3)
       EDS0071 (3) EDS0072 (3) MAX31826 (3)

   Humidity
       DS1922 (3) DS2438 (3) EDS0065 (3) EDS0068 (3)

   Voltage
       DS2450 (3)

   Resistance
       DS2890 (3)

   Multifunction (current, voltage, temperature)
       DS2436  (3)  DS2437  (3) DS2438 (3) DS2751 (3) DS2755 (3) DS2756 (3) DS2760 (3) DS2770 (3)
       DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)

   Counter
       DS2423 (3)

   LCD Screen
       LCD (3) DS2408 (3)

   Crypto
       DS1977 (3)

   Pressure
       DS2406 (3) TAI8570 (3) EDS0066 (3) EDS0068 (3)

   Moisture
       EEEF (3) DS2438 (3)

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Paul Alfille (paul.alfille@gmail.com)